A couple of us from the London Hackspace got invited to build and demo a machine for BBC Click ( on BBC world services). We threw together a machine that listens for tweets, dispenses a ball into a holding area and then at the end of the show fires them into the audience.

Heres a few pics

Heres the complete setup

A nice closeup of the Ball Holding area (thrown together in half an hour with a glue-gun)